The present invention relates to an airbag cushion which exhibits a low amount of seam usage (in order to attach at least two fabric panels or portions of a panel together) in correlation to an overall high amount of available inflation airspace within the cushion itself. These correlated elements are now combined for the first time in what is defined as an effective seam usage index (being the quotient of the length of overall seams on the cushions and the available inflation airspace volume). The inventive cushion must have at least one substantially straight seam and must possess an effective seam usage factor of less than about 0.11. A cushion exhibiting such a low seam usage factor and also comprising an integrated looped pocket for the disposition of an inflator can is also provided as well as an overall vehicle restraint system comprising the inventive airbag cushion.
Inflatable protective cushions used in passenger vehicles are a component of relatively complex passive restraint systems. The main elements of these systems are: an impact sensing system, an ignition system, a propellant material, an attachment device, a system enclosure, and an inflatable protective cushion. Upon sensing an impact, the propellant is ignited causing an explosive release of gases filing the cushion to a deployed state which can absorb the impact of the forward movement of a body and dissipate its energy by means of rapid venting of the gas. The entire sequence of events occurs within about 30 milliseconds. In the undeployed state, the cushion is stored in or near the steering column, the dashboard, in a door, or in the back of a front seat placing the cushion in close proximity to the person or object it is to protect.
Inflatable cushion systems commonly referred to as air bag systems have been used in the past to protect both the operator of the vehicle and passengers. Systems for the protection of the vehicle operator have typically been mounted in the steering column of the vehicle and have utilized cushion constructions directly deployable towards the driver. These driver-side cushions are typically of a relatively simple configuration in that they function over a fairly small well-defined area between the driver and the steering column. One such configuration is disclosed in U.S. Pat. No. 5,533,755 to Nelsen et al., issued Jul. 9, 1996, the teachings of which are incorporated herein by reference.
Inflatable cushions for use in the protection of passengers against frontal or side impacts must generally have a more complex configuration since the position of a vehicle passenger may not be well defined and greater distance may exist between the passenger and the surface of the vehicle against which that passenger might be thrown in the event of a collision. Prior cushions for use in such environments are disclosed in U.S. Pat. No. 5,520,416 to Bishop, issued May 28, 1996; U.S. Pat. No. 5,454,594 to Krickl issued Oct. 3, 1995; U.S. Pat. No. 5,423,273 to Hawthorn et al. issued Jun. 13, 1995; U.S. Pat. No. 5,316,337 to Yamaji et al. issued May 31, 1994; U.S. Pat. No. 5,310,216 to Wehner et al. issued May 10, 1994; U.S. Pat. No. 5,090,729 to Watanabe issued Feb. 25, 1992; U.S. Pat. No. 5,087,071 to Wallner et al. issued Feb. 11, 1992; U.S. Pat. No. 4,944,529 to Backhaus issued Jul. 31, 1990; and U.S. Pat. No. 3,792,873 to Buchner et al. issued Feb. 19, 1974, all of which are incorporated herein by reference.
The majority of commercially used restraint cushions are formed of woven fabric materials utilizing multifilament synthetic yarns of materials such as polyester, nylon 6 or nylon 6,6 polymers. Representative fabrics for such use are disclosed in U.S. Pat. No. 4,921,735 to Bloch issued May 1, 1990; U.S. Pat. No. 5,093,163 to Krunimheuer et al. issued Mar. 3, 1992; U.S. Pat. No. 5,110,666 to Menzel et al. issued May 5, 1992; U.S. Pat. No. 5,236,775 to Swoboda et al. Aug. 17, 1993; U.S. Pat. No. 5,277,230 to Sollars, Jr. issued Jan. 11, 1994; U.S. Pat. No. 5,356,680 to Krummheuer et al. Oct. 18, 1994; U.S. Pat. No. 5,477,890 to Krummheuer et al. issued Dec. 26, 1995; U.S. Pat. No. 5,508,073 to Krummheuer et al., issued Apr. 16, 1996; U.S. Pat. No. 5,503,197 to Bower et al. issued Apr. 32, 1996 and U.S. Pat. No. 5,704,402 to Bowen et al. issued Jan. 6, 1998, all of which are incorporated herein by reference.
As will be appreciated, the permeability of the cushion structure is an important factor in determining the rate of inflation and subsequent rapid deflation following the impact event. In order to control the overall permeability of the cushion, it may be desirable to use differing materials in different regions of the cushion. Thus, the use of several fabric panels in construction of the cushion may prove to be a useful design feature. The use of multiple fabric panels in the cushion structure also permits the development of relatively complex three dimensional geometries which may be of benefit in the formation of cushions for passenger side applications wherein a full bodied cushion is desired. While the use of multiple fabric panels provides several advantages in terms of permeability manipulation and geometric design, the use of multiple fabric panels for use in passenger side restraint cushions has historically required the assembly of panels having multiple different geometries involving multiple curved seams.
As will be appreciated, an important consideration in cutting panel structures from a base material is the ability to maximize the number of panels which can be cut from a fixed area through close-packed nesting of the panels. It has been found that minimizing the number of different geometries making up panels in the cushion and using geometries with substantially straight line perimeter configurations generally permits an enhanced number of panels to be cut from the base material. The use of panels having generally straight line profiles has the added benefit of permitting the panels to be attached to one another using substantially straight seams or be substantially formed during the weaving process using a jacquard or dobby loom. For the purposes of this invention, the term xe2x80x9cseamxe2x80x9d is to be understood as any point of attachment between different fabric panels or different portions of the same fabric panel. Thus, a seam may be sewn (such as with thread), welded (such as by ultrasonic stitching), woven (such as on a jacquard or dobby loom, as merely examples), and the like. The key issue regarding seam length within this invention pertains to the ability to form a high available inflation airspace volume cushion with the lowest amount of labor needed. Since sewing, welding, etc., procedures to connect panels or portions of panels greatly increases the time necessary to produce airbag cushions, it is highly desirable to reduce the labor time which can be accomplished through the reduction in the length of seams required. Substantially straight seam configurations thus provide more cost-effective methods of producing such airbags.
However, even with the utilization of substantially straight seams to produce airbags cushions, a problem still resides in the need for labor-intensive cutting and sewing operations for large-scale manufacture. There remains a need then to reduce the amount of time to produce airbag cushions while simultaneously providing the greatest amount of fabric to allow for a sufficient volume of air (gas) to inflate the target airbag cushion during an inflation event (herein described as xe2x80x9cavailable inflation airspacexe2x80x9dxe2x80x9d). Such a desired method and product has not been available, particularly for passenger-side airbags which, as noted previously, require greater amounts of fabric for larger volumes of air (gas) to provide the greatest amount of protection area to a passenger. With greater amounts of fabric needed, generally this has translated into the need for longer seams to connect and attach fabric panels, which in turn translates into greater amounts of time needed for sewing, and the like, operations. Thus, a need exists to produce high available inflation airspace volume airbag cushions with minimal requirements in seam lengths to manufacture the overall cushion product. The prior art has not accorded any advancements or even discussions to this effect.
In view of the foregoing, it is a general object of the present invention to provide a cost-effective, easy to manufacture airbag cushion for utilization within a vehicle restraint system. The term vehicle restraint system is intended to mean both inflatable occupant restraining cushion and the mechanical and chemical components (such as the inflation means, ignition means, propellant, and the like). It is a more particular object of the present invention to provide a vehicle restraint system wherein the target airbag cushion preferably requires all substantially straight seams to attach its plurality fabric components together (although as noted above, other configured seams may also be used as long the overall required effective seam usage factor is met). A further object of this invention is to provide an easy-to-assemble airbag cushion which is minimally labor-intensive to manufacture, which also comprises an integrated looped pocket for the disposition of an inflator can within the airbag cushion. It is still a further object of this invention to provide a vehicle restraint system comprising an airbag cushion which provides the maximum amount of available inflation airspace volume simultaneously with the lowest length of seam (or seams) necessary to manufacture the cushion. Another object of the invention is to provide a method of making a low cost airbag cushion (due to low levels of labor required to sew the component parts together) of simple and structurally efficient design.
To achieve these and other objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the present invention provides an airbag cushion having at least one substantially straight seam, wherein said airbag cushion possesses an effective seam usage factor of less than about 0.11, wherein said seam usage factor is derived from a seam usage index which concerns (and is defined as) the quotient of the total length of all seams present within the airbag cushion (measured in meters) over the total volume of available inflation airspace within the airbag cushion (measured in liters). As noted above, the seam itself may be applied by any well known operation including, but not limited to, thread-stitching, ultrasonic stitching, and the like, or could be woven within the fabric on a jacquard or dobby loom, and the like. The term xe2x80x9cavailable inflation airspace,xe2x80x9d as eluded to above, connotes the volume within which air (gas) would be transferred from an inflation assembly to the airbag cushion during and inflation, and consequent, inflation event. Such an airbag cushion must generally have at least one substantially straight seam, although, preferably, each seam possesses such a specific configuration. In order to produce such a specific airbag cushion, in fact, it is evident that the amount of sewing, stitching, and the like, required to form the end-product must be very low. A curved seam, although possible in this invention, requires potentially longer lengths of thread, etc., in order to attach the different fabric components of the target cushion. As a result, the utilization of curved, or other non-straight seams, should be minimized.
The effective seam usage factor (as defined within the correlating seam usage index formula, above) for the inventive airbag cushion then is preferably less than about 0.10, more preferably less than 0.09, still more preferably less than 0.07, even more preferably less than 0.06, and most preferably lower than 0.05. Thus, the volume of available inflation airspace within the airbag cushion should be as great as possible with the length of seam reduced to its absolute minimum.
A one-piece construction will generally have a relatively low available inflation airspace volume, although the length of the total number of seams may be quite low; a driver-side airbag will generally consist of many seams (of relatively large overall length), particularly curved seams, and a correlative relatively low volume of available airspace; and the prior art passenger-side airbags require complex sewing operations with numerous and rather long seams. Although the available inflation airspace volume in such passenger-side airbags is rather large, the total length of all the utilized seams is generally too great to meet the aforementioned effective seam usage factor within the index.
The present invention also provides an airbag cushion possessing the required effective seam usage factor which also comprises a looped pocket for introduction of the inflator can of an inflator assembly. In the most preferred embodiment one large body panel is utilized having two mirror-image portions which, when folded over along the middle of the fabric panel, the boundaries of both portions are aligned. One substantially straight seam is then utilized to seal the adjacent (and similarly configured) side to the already-folded side and two opening will remain. The large opening is then covered by one panel of rectilinear shape; the small opening (opposite the large opening) will have extra fabric which can be overlapped (to provide extra reinforcing fabric at the point of potential inflation) and sewn to form the desired pocket in which to dispose the inflation can. This embodiment is discussed below in greater detail.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice for the invention. It is to be understood that both the foregoing general description and the following detailed description of preferred embodiments are exemplary and explanatory only, and are not to be viewed as in any way restricting the scope of the invention as set forth in the claims.